Examples of typical known wireless power transmission systems include magnetic-field coupling power transmission systems in which power is transmitted from the primary coil of a power transmitting apparatus to the secondary coil of a power receiving apparatus through a magnetic field. In these systems, when power is transmitted through magnetic-field coupling, the strength of magnetic flux passing through the coils strongly influences electromotive force and, hence, high-accuracy relative positional relationship between the primary coil and the secondary coil is required. Further, it is difficult to reduce the size of the apparatuses, since coils are used.
On the other hand, an electric-field coupling wireless power transmission system such as the one disclosed in Patent Document 1 is also known. The power transmission system disclosed in Patent Document 1 is formed of a power transmitting apparatus and a power receiving apparatus each including a passive electrode and an active electrode. As a result of the active electrode of the power transmitting apparatus and the active electrode of the power receiving apparatus being placed close to each other with a gap therebetween, a strong electric field is formed between these two electrodes, whereby the electrodes are coupled through an electric field. Hence, high-efficiency power transmission is realized between the power transmitting apparatus and the power receiving apparatus. In this system disclosed in Patent Document 1, the required accuracy of the relative positional relationship between the coupling electrodes is comparatively low, and it is possible to make the sizes and thicknesses of the coupling electrodes small.
Patent Document 1: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2009-531009
Examples of such a power receiving apparatus include electronic apparatuses such as a cellular phone and a personal digital assistant (PDA). In recent years, these electronic apparatuses employ a user friendly capacitive input unit (touch panel) in many cases. When a power receiving apparatus includes a touch panel, the power receiving apparatus may be in a state in which the touch panel is operated while the power receiving apparatus is mounted on the power transmitting apparatus and is being charged. However the power receiving apparatus may malfunction due to an electric field formed by the active electrodes of the power transmitting apparatus and the power receiving apparatus as described above.